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US4790203A - Worm gear - Google Patents

Worm gear Download PDF

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Publication number
US4790203A
US4790203A US07/106,607 US10660787A US4790203A US 4790203 A US4790203 A US 4790203A US 10660787 A US10660787 A US 10660787A US 4790203 A US4790203 A US 4790203A
Authority
US
United States
Prior art keywords
thread
threads
worm gear
nut
support projection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US07/106,607
Other languages
English (en)
Inventor
Manfred Brandenstein
Horst-Manfred Ernst
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SKF GmbH
Original Assignee
SKF GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SKF GmbH filed Critical SKF GmbH
Assigned to SKF GMBH reassignment SKF GMBH ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: BRANDENSTEIN, MANFRED, ERNST, HORST-MANFRED
Application granted granted Critical
Publication of US4790203A publication Critical patent/US4790203A/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/24—Elements essential to such mechanisms, e.g. screws, nuts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/18—Mechanical movements
    • Y10T74/18568—Reciprocating or oscillating to or from alternating rotary
    • Y10T74/18576—Reciprocating or oscillating to or from alternating rotary including screw and nut
    • Y10T74/1868—Deflection related
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/19—Gearing
    • Y10T74/19642—Directly cooperating gears
    • Y10T74/19698—Spiral
    • Y10T74/19702—Screw and nut
    • Y10T74/19721—Thread geometry

Definitions

  • This invention relates to worm gears, and is more particularly directed to improvements in the shape of the threads of worm gear for the purpose of, for example only, avoiding clamping of the threads thereof when the gears are subject to inclined forces.
  • a worm gear of known type such as disclosed, for example, in U.S. Pat. No. 4,679,458, is advantageously employed for the translation of rotational movements to linear movements.
  • the function of this gear can be reversed, i.e. to translate linear movements to rotational movements.
  • the threads have trapezoidal cross sections, whereby relatively large surface thread flanks are provided, thereby attaining a higher load carrying capacity. Under axial loading it is attampted as much as possible for the loading to be distributed over the entire thread length.
  • the threads of the spindle and of the nut must be made with extremely low tolerance.
  • the spindle is provided in many cases with minimum axial play with respect to the nut, whereby a minimum gap results between the unloaded thread flanks under pure axial force.
  • the gap occurs on the other thread flanks of the outer and inner threads under reverse axial loading.
  • both thread flanks of the inner threads are in contact with the corresponding flanks of the outer threads at the corresponding circumferential positions of the threads.
  • the known arrangement is so constructed that in this case for example a contact occurs in the region of the loaded thread flanks between the thread crown surface of the inner thread and the groove bottoms of the outer threads.
  • This object is solved by providing the thread flanks of at least one thread with a convex cross section in the radial direction and providing the groove bottom of at least one thread with a central extending support projection, and by providing a radially deeper edge region on both sides of the projection, whereby between the transition region of the thread flanks to the thread crown surface of the one thread and the bottom surface of the edge region of the other thread at least a minimum gap is provided, when the maximum inclined position of the threads with respect to one another occurs.
  • the ability of the threads to move freely while in relatively inclined positions is consequently improved.
  • the support projection in the center of the groove bottom serves for the radial support for the crown surface of the other thread.
  • the corresponding transition regions of these threads between the thread flanks and the crown surfaces can thereby extend without contact in the free space formed between the support projection and the laterally adjacent, radially deeper edge regions. Precise formation of the edge regions is thereby not only not necessary with respect to the dimensions but also not necessary with respect to the outer surface quality.
  • Only the running surface of the support projection need be precisely formed in order to produce a smooth sliding movement also during the occurrence of inclined position. It is thereby expedient to round the edge surfaces of the threads.
  • a completely convex rounding is, according to a further feature of the invention, especially advantageous.
  • the thread flank of the other thread lying on the convex cross section thread flank of the one thread is curved with a comparatively larger radius.
  • FIG. 1 is a partial lengthwise cross sectional view of a worm gear in accordance with the invention:
  • FIG. 2 is an enlarged lengthwise cross section view of a thread of the worm gear of FIG. 1, with uniform radial loading;
  • FIG. 3 is a cross section view of the thread as shown in FIG. 2, but with inclined positions of the threaded spindle with respect to the nut.
  • the worm gear illustrated in FIG. 1 is comprised of a threaded spindle 1 and a nut 2, coupled to one another by substantially trapezoidal threads.
  • the inwardly directed threads 3 of the nut 2 and the outwardly directed threads 3 of the threaded spindle 1 are so dimensioned, with respect to one another, that axial as well as radial play is provided. If the threaded spindle 1, as shown, is axially forced against the nut 2 with a force F as shown, the inclined thread flanks 5 produce a centering action, so that at least theoretically a constant gap 4 occurs over the whole circumference, corresponds to the radial play.
  • one of the thread flanks 5 runs along the entire length of the threads 3 inside of the nut in contact with the corresponding thread flank 5 of the threaded spindle 1.
  • the pitch of the threads 3 is relatively large, whereby the nut 2 experiences a turning moment in response to the force F.
  • the radial and axial play have a predetermined relationship to one another. This is apparent in FIG. 2, wherein the upper left threaded region 7 of FIG. 1 of the threaded spindle 1 and the corresponding section of the thread groove 8 of the nut 2 are illustrated. Radial forces F act on the threaded spindle 1 acting in the same direction, whereby the spindle is displaced radially toward the nut 2 an amount equal to the radial play. Consequently the gap 4 disappears and the thread crown surface 9 engages the groove bottom 10. The axial play in this position is not very large, so that a gap remains between the thread flanks. In FIG. 2 the gap 6 only shown on the right thread flank 5 for clarity, at which position it is recognizably distinct.
  • the gap 6 can occur equally as well on the left thread flank 5 in response to the opposite axial force.
  • the groove bottom 10 is provided with an axially central radially inwardly extending support projection 11.
  • a radially deeper corner region 20 (i.e. having a greater diameter) is adjacent the projection 11 on both sides thereof.
  • the profile of the support projection 11 is convexly rounded.
  • the thread flanks 5 of the nut 2 are slightly convexly rounded, 21, in the radial direction.
  • FIG. 3 illustrates the left upper region of the worm gear of FIG. 1 with an inclined position between the nut 2 and the threaded spindle 1 in response to a tipping force F as shown.
  • the axes of symmetry of thread motion of the nut 2 and the threaded spindle 1 are at a slight angle to one another. Due to the convex curvature of the thread flanks 5 of the nut 2, there also exists in this inclined position the same contact relationship as existed in the non-inclined condition of FIG. 2. There is consequently no great differential surface force as in the case of conventional threads.
  • the threads 3 are dimensioned so that even in the maximum inclined position according to FIG.
  • the width 22 of the support projection is preferrably about one third of the entire width 23 of the groove bottom.
  • the thread 24, other than the convexly curved one thereof whose crown engages the support projection has a convex surface (not shown) with a radius greater than that of the thread which it engages.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)
  • Gears, Cams (AREA)
  • Gear Transmission (AREA)
US07/106,607 1986-10-15 1987-10-08 Worm gear Expired - Fee Related US4790203A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863635040 DE3635040A1 (de) 1986-10-15 1986-10-15 Schraubengetriebe
DE3635040 1986-10-15

Publications (1)

Publication Number Publication Date
US4790203A true US4790203A (en) 1988-12-13

Family

ID=6311740

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/106,607 Expired - Fee Related US4790203A (en) 1986-10-15 1987-10-08 Worm gear

Country Status (6)

Country Link
US (1) US4790203A (de)
JP (1) JPS63152768A (de)
DE (1) DE3635040A1 (de)
FR (1) FR2605375B1 (de)
GB (1) GB2197706B (de)
IT (1) IT1222902B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5934144A (en) * 1996-06-10 1999-08-10 Active Automation, Inc. Split gear assembly for use in a worm gear drive
EP0959271A2 (de) 1998-05-18 1999-11-24 Teleflex Incorporated Spiralförmige Kabelbetätigung für Kabelschaltzug
US20080029728A1 (en) * 2006-08-04 2008-02-07 Vetco Gray Inc. High Aspect Ratio Threadform
US20200340517A1 (en) * 2017-11-16 2020-10-29 Physik Instrumente (Pi) Gmbh & Co. Kg Spindle nut

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2233061B (en) * 1989-06-20 1993-01-20 Mabey Hire Co Screw threads
DE102015212448B4 (de) * 2015-07-02 2020-07-02 Zf Friedrichshafen Ag Spindelantrieb und Aktuator mit einem Spindelantrieb
WO2018068778A1 (de) * 2016-10-10 2018-04-19 Grammer Ag Getriebe sowie kopfstütze mit wenigstens einem elektrischen antrieb, umfassend ein getriebe

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2171171A (en) * 1985-02-16 1986-08-20 Skf Gmbh First and second screw-threaded elements

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1043743B (de) * 1956-03-06 1958-11-13 Carl Bruno Strandgren Differentialrollenschraubentrieb
GB952782A (en) * 1961-11-08 1964-03-18 Vickers Armstrongs Aircraft Improvements in screw-and-nut assemblies
US3323402A (en) * 1965-10-08 1967-06-06 Standard Pressed Steel Co Thread forms
US4036110A (en) * 1975-11-14 1977-07-19 General Motors Corporation Power steering gear with piston nut and screw operatively connected by centralizing root diameter thread

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2171171A (en) * 1985-02-16 1986-08-20 Skf Gmbh First and second screw-threaded elements
US4679458A (en) * 1985-02-16 1987-07-14 Skf Gmbh Worm gear

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5934144A (en) * 1996-06-10 1999-08-10 Active Automation, Inc. Split gear assembly for use in a worm gear drive
EP0959271A2 (de) 1998-05-18 1999-11-24 Teleflex Incorporated Spiralförmige Kabelbetätigung für Kabelschaltzug
US20080029728A1 (en) * 2006-08-04 2008-02-07 Vetco Gray Inc. High Aspect Ratio Threadform
US7819385B2 (en) * 2006-08-04 2010-10-26 Vetco Gray Inc. High aspect ratio threadform
US20200340517A1 (en) * 2017-11-16 2020-10-29 Physik Instrumente (Pi) Gmbh & Co. Kg Spindle nut
US11885367B2 (en) * 2017-11-16 2024-01-30 Physik Instrumente (Pi) Gmbh & Co. Kg Spindle nut

Also Published As

Publication number Publication date
GB8724115D0 (en) 1987-11-18
FR2605375B1 (fr) 1990-12-07
IT8722262A0 (it) 1987-10-14
IT1222902B (it) 1990-09-12
JPS63152768A (ja) 1988-06-25
DE3635040C2 (de) 1990-03-22
GB2197706B (en) 1990-05-30
DE3635040A1 (de) 1988-04-21
FR2605375A1 (fr) 1988-04-22
GB2197706A (en) 1988-05-25

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Legal Events

Date Code Title Description
AS Assignment

Owner name: SKF GMBH, ERNST-SACHS STR. 2-8, 8720 SCHWEINFURT 2

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:BRANDENSTEIN, MANFRED;ERNST, HORST-MANFRED;REEL/FRAME:004774/0820

Effective date: 19870930

Owner name: SKF GMBH,GERMANY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BRANDENSTEIN, MANFRED;ERNST, HORST-MANFRED;REEL/FRAME:004774/0820

Effective date: 19870930

REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
FP Lapsed due to failure to pay maintenance fee

Effective date: 19921213

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362